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Dethridge, John Stewart (1865–1926)

John Stewart Dethridge (1865-1926), civil engineer, was born on 25 June 1865, at South Yarra, Melbourne, son of James Dethridge, a clerk in the Department of Posts and Telegraphs, and his wife Mary, née Kipling. His elder brother was Judge George James Dethridge. John left school early and entered the building trade. In April 1888 he joined the Department of Public Works as an inspector of works, and five years later he was promoted to the Mines and Water Supply Department as inspector-in-charge of the Coliban water-supply and irrigation system.

In 1897 Dethridge passed his water-supply examinations, which qualified him for the professional division, and in 1899 he resigned his permanent appointment in the general division to accept a temporary appointment as assistant engineer. He became a permanent professional officer in 1902. At this time he was overseeing the works being executed by the Mildura Irrigation Trust.

In 1903 Dethridge was appointed executive engineer for the Goulburn River works, which included the Nagambie Weir and the Waranga Basin. He was responsible for the raising of the Waranga embankment and for the design of the Sugarloaf Weir. During his years of close association with the Goulburn irrigation system he developed his direct measuring water-meter for use in flood irrigation, a simple, robust and inexpensive device which he refused to patent. It became standard throughout the Victorian irrigation areas, and has been widely adopted overseas.

In April 1907 Dethridge was promoted to engineer and given charge of the Carrum as well as the Goulburn-Waranga works. Next year he became deputy chief engineer of the department, the senior professional officer concerned with irrigation. In 1911 he was appointed to a vacancy as one of the three commissioners of the recently formed State Rivers and Water Supply Commission. For four years he served under the chairmanship of Elwood Mead, an eminent engineer. But in 1915, when W. Cattanach took over as chief commissioner, Dethridge became the senior engineer in the commission. His engineering ability was of special significance to Victoria during the next eleven years, which saw the doubling of the water storage of the State.

Dethridge was the Victorian representative at the Interstate Conference of Engineers (1913) which formulated the River Murray Agreement. When the River Murray Commission was set up on 1 February 1917 Dethridge acted for his State. In the next few years the Murray was regulated by a series of locked weirs, of which Dethridge designed two, those at Torumbarry, below Echuca, and at Mildura. These were novel structures. Each consisted of a row of steel trestles mounted on wheels so that they could be rolled completely out of the river in time of flood.

Dethridge was also associated with the first Eildon Reservoir and the Pyke's Creek and Melton reservoirs on the Werribee River. He was an active member of the Institution of Civil Engineers (London), to which he had been elected in 1909, and was chairman of the local association of the institution in 1923-24.

Dethridge had not yet yet retired when he died on 15 May 1926 at his house at Brighton Beach, after an illness of some months. He was survived by his wife, the former Margaret Robinson of Horsham, whom he had married on 30 October 1895, and by nine of his eleven children.

John Dethridge's all-round ability is shown by his rise to professional status from his early occupation as a building worker, and by his advancement from assistant engineer to commissioner in only twelve years. He was admired and liked even by the most junior members of his staff—which was a rarity in those days. His Eildon Weir has been submerged by the much larger Eildon Dam, but most of his works survive as his monuments, as do the ubiquitous Dethridge water-meters; and his ingenious weirs on the Murray are in full use after many decades.

Select Bibliography

Aqua, Mar 1958

Age (Melbourne), 17 May 1926

Argus (Melbourne), 17 May 1926.

Citation details

Ronald McNicoll, 'Dethridge, John Stewart (1865–1926)', Australian Dictionary of Biography, National Centre of Biography, Australian National University, http://adb.anu.edu.au/biography/dethridge-john-stewart-5966/text10181, published first in hardcopy 1981, accessed online 22 March 2019.

This article was first published in hardcopy in Australian Dictionary of Biography, Volume 8, (MUP), 1981